1. Field of the Invention
The invention relates to a wrench which is useful for tightening and loosening locknuts on cable clamps or conduits used with electrical boxes.
2. Description of the Prior Art
The problem addressed by this invention is loosening and tightening lock nuts on cable clamps or conduit that are used to secure electrical cables or conduits on entry into and exit from electrical boxes, such as breaker boxes, service entry boxes, and junction boxes. A lock nut (or ring) is an annular ring having a series of protrusions also known as ears around its outer periphery and internal threads that define a circular central opening inside the threads. Lock nuts are used to secure conduit or cable to a “knock out” hole in an electrical box. In the case of securing cable, a cable clamp is used. A cable clamp is a device that slips over an electrical cable having one end section that clamps onto the cable, a second end section that is a cylinder threaded on the outside to accept a lock nut, and a flange between the two end sections. The cable clamp is placed onto the cable, a free end of the cable is fed through one of a number of circular openings located at various positions around the top, bottom, sides and back of the box with the clamping end outside the box and the threaded portion of the cable clamp extending into the box through the circular opening. An installer must access the interior of the box through a generally rectangular panel on the front of the box. The lock nut is threaded onto the threaded portion of the cable clamp until the cable clamp is secured onto the box with the flange on the outside and the lock nut on the inside. The lock nut is then tightened by placing the blade of a screwdriver onto one of the tabs of the lock nut and striking the screw driver with a hammer in a direction which will tighten the lock nut. When conduit is routed into a box, a threaded fitting is attached to the end of the conduit that serves the same purpose as the cable clamp for routing cable. The threaded end is secured with a lock nut inside the box, which is tightened as with the lock nut on cable clamp.
In order to remove the cable or conduit the procedure is reversed. The lock nut is loosened by placing the blade of a screwdriver onto a tab of the lock nut and striking the screwdriver with a hammer in a direction that will loosen the lock nut.
The problem to be solved by the instant invention is tightening and loosening lock nuts, particularly the hammer—screwdriver procedure that is ubiquitous at construction sites. The problem is exacerbated by the fact that electrical boxes often provide very tight quarters in which to work, and there is not always direct access to a particular opening through the front panel. For instance, an opening may be displaced left or right, up or down, and there may be a lip around the panel that must be traversed to reach an opening. There may also be several rows of openings on an edge, and wires may be installed at each position.
Several possible solutions to this problem have been disclosed in the patent literature.
U.S. Pat. No. 1,752,074 to Gagne is a spanner wrench that can be used to tighten or loosen toothed nuts.
U.S. Pat. No. 2,522,038 to Houghton is a wrench designed for use in a junction box, comprising a cage structure attached to a shank with a universal joint, where the cage structure has an annular member with lugs for engaging a nut with teeth.
U.S. Pat. No. 3,768,345 to Barnes is a spanner type drive head having teeth to mate the serrations of a lock nut and having an aperture to accommodate cable.
U.S. Pat. No. 5,524,511 to Takas is a lock nut wrench for conduit comprising a “C” shaped head attached at the center of the “C” to a member which is pivotably attached to a shank of a handle, such that the head extends at an angle from the shaft to provide clearance between the handle and the surface upon which a lock nut is to be tightened. The “C” shaped head is formed to engage the lock nut on a step around its interior surface and provides an opening in the head to fit over a piece of conduit.
U.S. Pat. No. 6,058,813 to Bryant is a lock nut wrench system for applying a proper rotational torque to a lock nut and ability to fit around adjacent wires during tightening and removal. The wrench is of the type with a cylindrical head which fits over a lock nut while having a wire port for passage of wires through the head. The head is pivotably attached to the handle.
U.S. Pat. Nos. 1,752,074, 2,522,038, 3,768,345, 5,524,511, and 6,058,813 referred to above are hereby incorporated herein by reference.
While the above improvements are all potential improvements to tightening and removing lock nuts in electrical boxes, there is still a need for an improved wrench which can be readily used to manipulate lock nuts in positions which are not directly accessible from the front panel opening of the electrical boxes.
There is a particular need for an improved wrench for tightening or removing lock nuts on cable clamps where the wires to be placed or removed are in a corner of an electrical box or behind another wire or group of wires.
There is a need for an improved wrench for tightening or removing lock nuts on cable clamps by accessing the lock not from the side rather than straight ahead or over top.